A. Field of the Invention
This invention relates to the field of art of hydraulic oscillators.
B. Prior Art
Hydraulic oscillators are known in the art and comprise a reciprocating piston within a cylinder controlled by a reversing valve such as a spool valve. For example, reciprocating piston oscillators are disclosed in the following U.S. Pat. Nos.:
3,450,349 PA1 3,643,548 PA1 3,780,622 PA1 3,786,723 PA1 3,896,889
However, the prior art hydraulic oscillators left much to be desired in applications which require continuous reciprocating motion at high volumetric efficiency as for example in supplying motive force to a cutter bar for a harvester. In such applications, it has been found herein that very fast tripping of a reversing valve is required to achieve rapid reversal of the pressurized main fluid flow to the cylinder housing the reciprocating piston. In this way, a hydraulic cushion must be provided in order to stop the piston short of its extreme travel position at either end of the cylinder or the piston would otherwise unacceptably strike the cylinder end. Another requirement is that the switching be accomplished without loss of pressure and with even pressure around the piston. Prior hydraulic oscillators have had many drawbacks and limitations in attempting to meet or even recognizing these stringent requirements.